The invention concerns conveyor systems for discrete entities, that is, for carrying individual items.
The invention will be more particularly described within the scope of its application to a container blow-molding facility in which the container is obtained by blowing a preform previously produced by injection.
However, the invention will find application in any conveyor system in which it is desired to merge in a single line and at a specific rate entities coming from several xe2x80x9csources.xe2x80x9d
Such a merging would be necessary, for example, in a facility when several slow-speed machines are used to perform the same step, in parallel, the entities being then all processed in a second step by a high-speed machine.
The example that will be described in detail is that of the feed for a preform temperature condition oven. Such an oven generally has a conveyor chain or wheel that transports the preforms in front of infrared lamps in order to bring them to a temperature at which the thermoplastic material becomes deformable for the last blow-molding operation.
The oven is usually fed with preforms by a single feed unit. This feed unit usually has a bin in which the preforms are stored in bulk, an inclined belt conveyor, a device to disentangle the preforms, and an inclined feed rail at the bottom of which the vertically oriented preforms are accumulated to form a buffer stock. At the bottom of this rail, an automatic gate allows a preform to pass at regular intervals, the preform then being engaged by a wheel with recesses.
Such feed units have the disadvantage of a lack of reliability at high speed, particularly because of the disentangling operation, which is very delicate.
Also, for the proper operation of the blow-molding facility, it is proposed here to feed the facility by two feed units that work in parallel. Each feed unit thus only has to provide half of the rate of the blow-molding facility.
However, it then becomes necessary to provide a conveyor system that merges the preforms furnished by the two feed units in such a way that at the oven, everything takes place as though the facility had a single feed unit.
This system should be simple, reliable and small in size.
The invention therefore proposes a system for conveying discrete entities, which system has a merging device fed by at least two upstream units each of which leads to the device for merging the entities that are spaced according to a first rate of speed, and of the type in which the entities leave the merging device in a single line at a second rate of speed, characterized in that the merging device has a merging wheel that is driven in rotation and is provided with several series of recesses that open radially toward to periphery of the wheel, in that the entities are each radially engaged from the exterior toward the interior in one recess, in that the recesses of a same series have the same radial depth, the series of recesses being differentiated by the depth of their recesses, in that each series of recesses is associated exclusively with one upstream unit.
According to other characteristics of the invention:
the different series of recesses fit into each other;
each upstream unit delivers its entities at a different loading point that occupies an angularly fixed position around the axis of the merge wheel, and the point of loading associated with the series of deepest recesses is placed the farthest upstream on the trajectory of the recesses of the merge wheel;
after the point of loading, the entity is guided between two internal and external slide rails that are placed in a plane axially offset with respect to the plane of the merge wheel, and the external slide rail forces the entity toward the bottom of the recess;
the difference in depth between two recesses of two different series is greater than the dimension of one entity in the radial direction;
the merging device has a slide rail which, on one part of the path of the wheel between the point of loading of the last series of entities and the point of discharge, cooperates with the entities to push them toward the peripheral edge of the merge wheel;
at least one of the upstream units has a wheel with recesses that is placed tangentially to the merge wheel; and
the entities are preforms for the blow-molding manufacture of containers from thermoplastic material.
The invention also proposes a facility for blow-molding containers from previously injected preforms, of the type having an oven for temperature conditioning the preforms, characterized in that the oven is fed with preforms by at least two feed units that are arranged in parallel and each of which delivers a series of regularly spaced preforms, and in that, between the feed units and the oven, the preforms are transported by a conveyor system incorporating any one of the preceding characteristics, the system merging the series of preforms in order to form a single series of preforms.